Pressure control with coarse and fine adjustment

ABSTRACT

A pressurization control system configured to regulate air pressure within a space includes a first damper fluidly coupled to an air supply, the first damper configured to control delivery of an air flow, and a second damper having an operating range, the second damper fluidly coupled to the air supply and the first damper, the second damper configured to supplement delivery of the air flow. The pressurization control system further includes a room controller configured to provide a control signal to the first and second dampers, wherein the control signal drives the first damper to direct the air flow towards the operating range, and wherein the control signal drives the second damper to direct the air flow towards a set point.

BACKGROUND

It is known to control and monitor the pressurization of a room and/orlaboratory to ensure occupant health and safety, as well as to protectsensitive manufactured products. Healthcare facilities and researchlaboratories may utilize complex pressurization schemes in order toprotect patients, personnel and researchers from hazardous viruses,pathogens, or other toxins. For example, a healthcare or researchfacility may seal and partially depressurize (generate a negative staticpressure) a room or laboratory that contains a hazardous material. Thus,if a breach or accident occurs, air would flow towards the hazardousmaterial, thereby containing and/or minimizing the potential spread orcontamination.

Biological laboratories are often maintained at a negative staticpressure specifically to prevent airflow out of the laboratory room.These laboratory rooms are constructed and classified as biosafety level1, 2, 3 and 4 based on, for example, the nature and danger associatedwith the work and materials housed within the laboratory. BiosafetyLevel 4 (BSL-4) is the highest safety level classification indicatingthe greatest risk to individuals within a laboratory itself, thefacility in which the laboratory is housed, and the surrounding areas.BSL-4 rated laboratories are constructed to be virtually leakproof,e.g., they are sealed so tightly that virtually no unintended airtransfer or release occurs, thus minimizing the chance of contaminantsescaping the laboratory. Alternatively, a BSL-4 rated laboratory couldbe a sealed room or enclosure into which another sealed, air tightcontainer is placed. Regardless, in an effort to control or prevent thespread of a hazardous contaminants, BSL-4 rated laboratories aretypically geographically isolated and operated at a high negative staticpressure, e.g., 0.1 to 0.5 inches w.c. or 25 to 125 Pa.

In order to ensure and control the airflow and ventilation within aBSL-4 rated laboratory, the mechanical ventilation system(s) supplyingthe laboratory will typically be designed and controlled to deliverdesired airflow rates and maintain selected pressure relationshipsbetween the laboratory and adjacent spaces. Certain pressurerelationships must be maintained or controlled during transientconditions such as, for example, changes in pressure caused by theopening of a door or entrance. Known laboratory pressurization schemessuch as, for example, differential flow control or airflow tracking areinapplicable in leakproof and/or sealed environments such as a BSL-4rated laboratory where the relative supply and exhaust airflows areconstant and may not be independently adjusted to establish a pressuredifferential. Similarly, direct pressure control and cascade pressureare unsuitable for tightly sealed environments where the transientconditions can severely and rapidly impact the desired pressurerelationship.

There exists a need for a pressurization scheme or strategy that may beutilized in a tightly sealed environment such as, for example, a BSL-4rated laboratory, to achieve and maintain a specific pressurerelationship.

BRIEF DESCRIPTION OF THE FIGURES

Additional features and advantages of the present embodiments aredescribed in, and will be apparent from, the following DetailedDescription and the figures.

FIG. 1 illustrates an embodiment of a laboratory in a first airflowconfiguration that utilizes the pressure control system disclosedherein;

FIG. 2 illustrates an embodiment of the laboratory in a second airflowconfiguration that utilizes the pressure control system disclosedherein; and

FIG. 3 illustrates a block diagram of a control scheme that may beutilized by a controller in one example.

DETAILED DESCRIPTION

In order to maintain a desired pressure or pressure differential withina pressure controlled room or laboratory, it may be desirable toimplement a pressure control system that utilizes a coarse flow controlvalve or damper in conjunction with a fine flow control valve or damper.Moreover, the coarse or first damper and the fine or second damper maybe controlled by a room controller configured to provide bothincremental flow and pressure control.

I. System Configuration

FIG. 1 illustrates one building layout 10 that may implement a pressurecontrol system disclosed herein. The building layout 10 includes a roomor laboratory 100 adjoined to a second room or airlock 200 via asealable doorway D. The laboratory 100 may include an air deliverysystem 102 fluidly coupled to an exhaust 104. The air delivery system102 and the exhaust 104, in this exemplary embodiment, may be configuredto generate a first negative pressure P1 in the laboratory 100. Thelaboratory 100 may be a “leakproof” or otherwise sealed room incompliance with BSL-4 safety standards. In other embodiments, thelaboratory 100 or other room may be sealed or have airflow regulated incompliance with other standards or specifications.

The airlock 200, similar to the laboratory 100, may include an airdelivery system 202 fluidly coupled to an exhaust 204. The air deliverysystem 202 and the exhaust 204, in this exemplary embodiment, may beconfigured to generate a second negative pressure P2 in the airlock 200.

In the present example, the environs (generally indicated by thereference identifier 300) surrounding the laboratory 100 and airlock 200will be assumed to be maintained generally at a third negative pressureP3. Moreover, as used throughout this exemplary embodiment, the pressuregradients between the three rooms or areas increase, e.g., become morenegative, based upon proximity to the laboratory 100. For example, usingthe air pressure at a non-hazardous point in the building selected asthe pressure reference, the third negative pressure P3 may be −25 Pa inthe environs 300, the second negative pressure P2 may be −50 Pa in theairlock 200, and the first negative pressure P1 may be −75 Pa in thelaboratory. Thus, if a leak or emergency occurs in the laboratory 100,the risk of contamination or escape of dangerous materials will bereduced because the pressure gradient will draw the air within theenvirons 300 and airlock 200 towards the laboratory 100 and thepotential hazards. This in-rush of air towards the laboratory 100prevents or limits the movement of the hazard towards the fluidlyconnected areas 200 and 300. In other words, in this configuration, airflows from areas of higher pressure, e.g., areas having less negativepressure, towards the partial vacuum within areas of lower pressure,e.g., areas that have a more negative pressure relative to the airsource.

The air delivery system 102 and the exhaust 104 may be, as shown,autonomous and/or isolated from the air delivery system 202 and theexhaust 204. Isolation of the two air delivery systems 102, 202 and/orexhausts 104, 204 may be desirable in order to preventcross-contamination of the two systems, limit the possibility of asimultaneous shutdown due to a system failure, and allow for independentcontrol of the airlock 200 and laboratory 100. Alternatively, the airdelivery system 102 and the exhaust 104 may be interconnected and/orfluidly coupled (not shown) to the air delivery system 202 and theexhaust 204. These systems 102, 202 and/or 104, 204 may be coupled,e.g., share a common air source and/or controller, to reduce the overallcost and complexity of the pressure control system.

In the present example, the air delivery system 102 and the exhaust 104are isolated from the air delivery system 202 and the exhaust 204. Theair delivery system 102 includes an air supply source 106 fluidlycoupled to a first air outlet or supply vent 108 via a main valve ordamper 110, and a second air outlet or supply vent 112 via a trim valveor damper 114. The air supply source 106 may be, for example, apropeller fan, a centrifugal fan, an air compressor or any other airmovement or pressure generation device. The main damper 110 may be amoveable or positionable valve or diaphragm positioned to deliver orsupply the majority of the air to the laboratory 100. In particular, themain air supply or air flow (indicated by the arrow Al) is suppliedthrough a duct 116 connecting the air supply source 106 to the airoutlet 108. The trim damper 114 may be a valve, diaphragm or dampersimilar to the main damper 110 configured and sized to deliver a small(compared to the air flow Al) or well-regulated amount of air to thelaboratory 100. For example, the regulated or supplemental air supply orair flow (indicated by the arrow A2), provided through a duct 118 andthe trim damper 114, supplements the main air supply Al thereby allowingfor fine flow and pressure adjustments to the overall pressure P1 of thelaboratory 100.

The air within the laboratory 100 fluidly couples the air supply 106 andair outlets 108, 112 to exhaust air flow El through the exhaust 104. Theexhaust air flow El, in turn, pulls the air within the laboratory 100from the room. The differential between the amount of flow of airprovided via the air flows A1 and A2 and removed from the exhaust airflow E1, e.g., removing more air than is provided, generates thenegative or vacuum pressure P1 within the laboratory 100. Pressure andflow sensors (not shown) may be positioned throughout the laboratory100, at the air outlets 108, 112 and/or the exhaust 104 to measure thepressure, air flow and air flow differential within or through thelaboratory 100.

A single room controller or controller 120 may be in communication withthe air delivery system 102 and the exhaust 104 to control the air flowsA1 and A2, and the exhaust air flow E1, respectively, within thelaboratory 100. Alternatively, separate controllers 120, 120′ (as shown)may be independently operating within the air delivery system 102 andthe exhaust 104, respectively, to provide for independent control ofthese air handling systems. In particular, the controller 120 mayutilize a processor (not shown) to execute control routines or programsstored on a computer readable medium or memory (not shown). The controlroutines may, in turn, calculate or otherwise determine the volume oramount of air to be provided by the air supply source 106.Alternatively, or in addition to, the control routines may calculate ordetermine the position of the main damper 110 and the trim damper 114necessary to achieve the desired air flows A1 and A2 through the outlets108, 112, respectively.

Similarly, the air delivery system 202 and the exhaust 204 includes anair supply source 206 fluidly coupled to a first air outlet 208 via amain damper 210, and a second air outlet 212 via a trim damper 214. Theair supply source 206 may be, for example, the same type or style of airsupply source 106 or may be a different source or generation system. Thedampers 210 and 214 may operate and/or cooperate in a manner similar tothe damper 108 and 112 to control and supply the main air flow A3 andthe regulated airflow A4. The air within the airlock 200 fluidly couplesthe air supply 206 and the first and second air outlets 208, 212 to theexhaust 204 via exhaust air flow E2. Similar to the laboratory 100,pressure and flow sensors (not shown) may be positioned throughout theairlock 200 to provide readings and measurements to a room controller orcontroller 220. The controller 220 may be in communication with the airdelivery system 102 and the controller 120 to regulate the air flows andpressures between the laboratory 100 and the airlock 200.

FIG. 1 further illustrates a steady state condition in which thelaboratory 100 is sealed and the air delivery system 102 and exhaust 104are operating independently from the airlock 200 and environs 300. Inparticular, in this situation the doorway D is closed, therebypreventing additional, higher pressure air from the airlock 200 fromuncontrollably flowing into or entering the laboratory 100. In thisconfiguration or state, the laboratory 100 is maintained at the pressureP1 by the cooperation of the airflows A1 and A2 provided via the maindamper 110 and the trim damper 114. For example, the main damper 110operates within a predefined operating range, e.g., a range defined bythe high and low airflow rates that may be established, to achieve orcreate a pressure differential at or about the desired pressure P1. Thepredefined operating range of the main damper 110 includes a deadbandbetween the high and low airflow limits and encompassing the desiredpressure P1 in which the coarse airflow Al is maintained at a constant.Once the main damper 110, and the provided coarse airflow A1, drives theroom pressure sufficiently towards the desired pressure P1 to enter thedeadband, the main damper 110 begins to maintain the airflow A1 at aconstant flow rate. At this point, the trim damper 114, which onlyoperates within the deadband of the main damper 110, begins to finelyadjust the airflow A2 to achieve the desired pressure P1. In otherwords, the main damper 110 operates to provide the airflow A1 sufficientto bring the laboratory pressure to within the effective operating rangeof the trim damper 114 which, in turn, provides an airflow A2 necessaryto achieve the desired pressure P1.

FIG. 2 illustrates a transient condition in which the doorway D to theairlock 200 is open or otherwise providing an additional airflow A tothe laboratory 100 in an uncontrolled manner. For the purposes of theexamples discussed herein, the additional airflow A is assumed to beprovided by the airlock 200 which is maintained at a constant pressureby the controller 220.

II. System Operation

FIG. 3 illustrates a room pressurization control routine 400 that may beimplemented by the controller 120 (or the controller 220). The roompressurization control routine 400 utilizes multiple control schemes ormechanisms to control or regulate the pressurization of the laboratory100 (or airlock 200) when the doorway D is closed. When the doorway D isopen, additional airflow A is provided to the laboratory 100 (or fromthe airlock 200). The room pressurization control routine 400 mayutilize: (a) a high flow feedback control algorithm 410; (b) a low flowfeedback control algorithm 420; (c) an incremental controller 430 incommunication with the high and low feedback control algorithms 410,420; and (d) a pressure feedback algorithm or controller 440. Theincremental controller 430 is configured to drive or control the main orcoarse damper 110 in response to incremental control signals provided bythe high and low feedback control algorithms 410, 420. The pressurefeedback algorithm or controller 440 is configured to independentlyregulate the fine or trim damper 114 in response to pressure controlsignal generated with respect to a pre-defined or desired pressureset-point. The pressure feedback algorithm or controller 440 may be aproportional-integral controller; a proportional-integral-differentialcontroller or a proportional-differential controller, or any other knowncontroller. The room pressurization control routine 400 may furtherinclude a comparator or comparator algorithm 450 configured to controlor regulate the interaction between the operating range and deadband ofthe main damper 110 and the operating range of the trim damper 114 whichcoincides with the deadband.

The control algorithms 410 and 420 operate to control the position ofthe damper 110 (and 210 if applicable) to thereby regulate the flow ofair, and ultimately the pressure, within the laboratory 100 (and airlock200 if applicable). However, only one of the three control algorithms410, 420 and 440 is selected by the incremental controller 430. Theselected control algorithm, in turn, determines the position of the maindamper 110 (and/or 210) during any given time or selection period. Forexample, the high and low flow feedback control algorithms 410 and 420may utilize and monitor the relative or differential air flows (e.g.,the difference between air flows A1 and exhaust air flow E1) within thelaboratory 100 in an effort to control or regulate the pressure P1.

The high and low flow feedback control algorithms 410 and 420 incooperation with the comparator algorithm 450 drive or alter the airflowA1 provided by the main damper 110 to establish an air flow differentialbetween the A1 and E1. As the air flow differential approaches thedesired pressure P1, the main damper 110 approaches a deadband withinits operating range. The deadband within the operating range of the maindamper 110, in turn, coincides with the operating range of the trimdamper 114. Within this deadband, the position, and hence the airflow A1provided by the main damper 110, is held constant in response to acommand, signal or instruction provided by the comparator 450, while thetrim damper 114, now within its effective operating range and under theoperational control of the pressure controller 440, makes the fine orfinal adjustments via the airflow A2 necessary to establish the desiredpressure P1 within the laboratory 100. The position or relative locationof the deadband (operating range of the trim damper 114) within theoperating range of the main damper 110 will typically be determined by apressure set point utilized by the pressure controller 440 andcorresponding to the desired pressure P1. For example, the pressure setpoint monitored by the pressure controller 440 may be established withinthe middle of the operating range of the trim damper 114 which, in turn,may be within the middle of the operating range of the main damper 110.In this way, the effectiveness of both the damper 110,114 may bemaximized by allowing the widest possible increase and decrease in theairflows A1, A2, respectively.

Some events may upset or disturb pressurization of the laboratory 100 ina way that requires a large change in air supply. For example, inresponse to a sudden decrease in pressure, the trim damper 114 may, inresponse to the pressure controller 440, shift to a position outside itsnormal operating range and away from the desired set point. The maindamper 110, no longer held in a constant position, shifts or opens inresponse to the incremental controller 430, thereby increasing theairflow A1 and causing the pressure to increase within the laboratory100. The pressure controller 440 responds by slowly closing orrestricting the airflow A2 provided by the trim damper 114 as thepressure P1 increases towards the desired set point. When the trimdamper 114 closes to a position within its operating range, e.g., thedeadband within the operating range of the main damper 110, the positionof the main damper 110 is locked or held, thereby preventing additionalchanges to the airflow A1. The trim damper 114, now acting within itsoperating range, continues to make the fine adjustments to the airflowA2 necessary to return the room pressure P1 to the desired set pointstored within the pressure controller 440. Thus, the main damper 10accomplishes large changes in overall supply flow (via the airflow Al),but does not directly interact or interfere with the small secondary ortrim damper 114. The dampers 110, 114 operate in the opposite directionif a change requires a large reduction in air supply.

A. Changes in Response to an Increase in Exhaust Airflow

In one exemplary embodiment, the laboratory 100 may be operated in a“constant volume” configuration, which ensures that the flow rate (theexhaust flow E1 and the combined supply flow A1/A2) therethrough remainsessentially unchanged or constant during normal operation. Normallylarge flow rate changes occur when the air delivery system 102 starts orstops. However, the exhaust 104 and/or other fluidly connected exhaustdevices such as, for example, an exhaust fan 122, may be started andstopped during routine operation of the air delivery system 102. It mayalso be possible for the flow rate to change in response to events thatoccur along the fluidly coupled central exhaust system. For example, ifthe exhaust 204 were fluidly coupled to the exhaust 104 along a centralconduit system, the operation of one of the exhausts will influence theoperation of the other. The influence or interrelated effects of thesetwo exhausts 104, 204, in this example, may be prevalent when thesystems are started or stopped with respect to each other. Theoccurrence of these transitory events may temporarily change the exhaustairflow E1 from the laboratory 100, and it may require a response orchange in the airflows A1 and A2 in response to the room pressurizationcontrol routine 400.

For example, when the laboratory 100 is operating in a normal, steadyoperating condition, the airflows A1 and A2 and the exhaust airflow E1are essentially steady or constant and near or at their respective setpoints. In this configuration or state, the pressure P1 within thelaboratory 100 is essentially steady or constant and near or at its setpoint. The trim damper 114 may be in a constant position or may makingsmall movements to adjust the airflow A2 within its operating range,i.e., the deadband of the main damper 110, and around the desiredpressure set point utilized by the pressure controller 440. Thus, innormal operation, the supply or main damper 110 is fixed in whateverposition it takes to deliver the airflow A1 that, along with the airflowA2 delivered through the trim damper 114, balances the exhaust E1.

When a disturbance occurs in the exhaust 104 or the laboratory 100 thatincreases the exhaust airflow E1, the supply airflows A1 and A2 are outof balance and the pressure P1 within the laboratory 100 will start todecrease. The room pressurization control routine 400, and in particularthe pressure controller 440, responds by opening the trim damper 114thereby increasing the airflow A2 in an attempt to balance the increasein exhaust E1. If the airflow A2 through the trim damper 114 matches orbalances the increase in exhaust E1 without leaving the operating rangeof the trim valve 114 (the deadband of the main damper 110), thenbalance may be restored and the flow rate within the laboratory 100 maybe maintained without adjusting the main damper 110.

If the increase or change in the position of the trim damper 114 and thecorresponding airflow A2 is not sufficient to balance the increase orchange in the exhaust E1, then the trim damper 114 keeps opening to thelimit of its operating range, thereby passing or exiting the deadband.This change reactivates the main damper 110 which allows for an increasein the airflow A1 as the damper opens. The increased airflow A1 providedby the main damper 110 has a greater effect on total supply airflow A1and A2 than the trim valve 114, and increases the flow rate enough tobalance the increased exhaust E1.

The increased total supply airflow A1 and A2 serves to bring thepressure P1 of laboratory 100 back toward the desired pressure set pointthereby causing the trim damper 114 to move towards the closed positionand decrease the airflow A2. As the trim damper 114 closes, it reentersits operating range or deadband, thereby locking the position of themain damper 110. The main damper 110 may be locked in response to acommand or signal provided by the comparator 450 or in response tocommands or signals provided by the pressure controller 440 orincremental controller 430. At this point, the pressure controller 440is in primary control of the room pressurization control routine 400 andcontinues to adjust or drive the trim damper 110 to bring the pressureP1 back to the set point. The trim damper 114 may end up near theoriginal position and the original airflow A1 before the change. Thetotal supply airflow Al and A2 ends up higher by approximately theamount of the increase of the exhaust E1. In this way, the main damper110 balances the increased exhaust E1.

B. Changes in Response to an Increase in Supply Airflow

In the exemplary embodiment shown in FIG. 2, the laboratory 100 isfluidly connected to the airlock 200 via the doorway D. In this example,the airlock has a higher pressure P2 relative to the pressure P1maintained in the laboratory 100. When the doorway between the rooms 100and 200 is sealed, there exists little or no airflow A therebetween.Thus, the laboratory 100 maintains a balance between the total supplyairflow A1 and A2 and the exhaust E1. In this configuration, theposition of the main damper 110 is fixed because all three of itscontrol functions are satisfied: (1) the high flow limit of the highflow feedback control algorithm 410 is above the current supply flowrate; (2) the low flow limit of the low flow feedback control algorithm420 is below the current supply flow rate; and (3) the trim damper 114is positioned within its operating range near its desired set point,well within the deadband as determined by the comparator 450.

When the doorway D opens to provide airflow A from the higher pressureairlock 200 to the laboratory 100, the opening (doorway D) is so largethat the pressures equalize (P1=P2) almost instantly and remainequalized as long as the doorway D remains open. Initially, that newpressure for the two rooms 100 and 200 equalizes to a pressure somewherebetween the original pressure levels P1 and P2 of the individual rooms100 and 200.

For the purpose of illustration, assume the higher-pressure airlock 200space remains at effectively a constant pressure P2 throughout the opendoorway D event. As discussed above, as soon as the doorway D opens andthe airflow A is provided to the laboratory 100, the pressure in thelaboratory 100 increases to match the other airlock 200 (the initialgust of airflow A at the higher pressure P2 supplies the air needed toraise the pressure P1 to the pressure P2). In response to the increasein pressure, the pressure controller 440 responds by driving the trimdamper 114 towards the closed position thereby limiting or reducing theairflow A2. As it does so, the total supply airflow A1 and A2 decreasesand no longer balances the exhaust E1. A draft through the doorway Ddevelops to make up the difference. The reduction in total supplyairflow A1 and A2 is compensated by increases in the airflow A providedthrough the doorway D, so even though the fine or trim damper 114 movestoward a closed position, and the total supply airflow A1 and A2decreases, the laboratory 100 pressure is maintained at higher pressureP2 of the airlock 200.

As the trim damper 114 closes in response to the pressure controller440, it passes out of its operating range, e.g., the deadband. Thistransition activates the main damper 110, which, in turn, starts toclose in an effort to restrict the airflow Al and reduce the pressurewithin the laboratory 100.

As the flow reduction continues, it approaches or passes the low flowlimit established within the low flow feedback control algorithm 420operating within the laboratory 100. At this point, the trim damper 114is fully closed. The pressure controller 440 continues to run, but hasno further effect on the laboratory 100. Thus the low flow feedbackalgorithm and the low flow limit directly control position and airflowAl provided by the main damper 110. If the doorway D remains open andcontinues to provide the airflow A for a sufficient period of time,pressure within the laboratory 100 will stabilize at the pressure P2 ofthe airlock 200. In this arrangement, the trim damper 114 is fullyclosed, the exhaust El may be maintained at its original rate, theairflow Al is provided at the low flow limit associated with the lowflow feedback control algorithm 420, and the airflow A operates as adraft through the doorway D to equalize the airflow between the exhaustEl and the low flow limit. This condition may be maintainedindefinitely, as long as the doorway D is open.

Upon closing of the doorway D, the airflow A is eliminated such that theexhaust E1 exceeds the total supply airflows A1 and A2 (A2 still beingeffectively at zero). This change in airflow results in a suddenpressure drop and the exhaust E1 removes air from the laboratory 100. Aspressure within the laboratory 100 approaches the set point associatedwith the pressure controller 440, the trim valve 114 is driven towardsits open position to supply positive airflow A2. As the trim damper 114opens and increases the airflow A2 in an attempt to compensate and matchthe exhaust E1, it may pass through the deadband established within theoperating range of the main damper 110 on the high side (e.g., theincreasing flow side) causing the main damper 110 to leave the low flowlimit of the low flow feedback algorithm 420 and to open to increase theairflow A1. This, in turn, increases the overall total supply airflow A1and A2 and moves pressure P1 of the laboratory 100 back to the set pointassociated with the pressure controller 440. The pressure controller440, in turn, responds by driving the trim damper 114 towards a closedposition and reducing the airflow A2 back towards the deadband.

While the doorway D was open, the switch to the low flow feed backalgorithm 420 prevents the main damper 110 from closing completely.This, in turn, limits the degree of control overshoot that occurs whenthe doorway D eventually closes.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present invention andwithout diminishing its intended advantages. It is therefore intendedthat such changes and modifications be covered by the appended claims.

What is claimed is:
 1. A pressurization control system configured toregulate air pressure within a room, the room comprising a closeabledoorway, the system comprising: a first damper fluidly coupled to an airsupply duct and having an operating range, the first damper configuredto control delivery of a main air flow directly to the room; a seconddamper having an operating range, the second damper fluidly coupled to asecond air supply duct, the second damper configured to control deliveryof a supplemental air flow directly to the room, the supplemental airflow being separate from the main air flow; and a room controllerconfigured to: provide a first control signal to the first damper and asecond control signal to the second damper, the provision of the firstcontrol signal comprising selection of a control scheme from a pluralityof control schemes the selection of the control scheme from theplurality of control schemes comprising selection of a high-flowfeedback control scheme, a low-flow feedback control scheme, or apressure feedback scheme to be run for a period of time, wherein in afirst configuration, the first control signal drives the first damper todirect the main air flow towards a deadband within the operating rangeof the first damper, the deadband within the operating range of thefirst damper including a pressure set point for the room, and when theair pressure within the room is within the deadband within the operatingrange of the first damper, the second control signal drives the seconddamper to direct the supplemental air flow towards the pressure setpoint for the room, and wherein in response to the closeable doorwayopening and the air pressure within the room increasing, the secondcontrol signal drives the second damper towards a closed position, andwhen the air pressure within the room exits the deadband, the firstcontrol signal drives the first damper towards a closed position until alow flow limit is reached.
 2. The system of claim 1, wherein the seconddamper is a trim valve.
 3. The system of claim 1, wherein the roomcontroller includes an incremental controller and a pressure controller.4. The system of claim 3, wherein the incremental controller isconfigured to generate an incremental control signal.
 5. The system ofclaim 3, wherein the pressure controller is configured to generate thesecond control signal, the second control signal being a pressurefeedback signal, and wherein the pressure feedback signal iscommunicated to the second damper.
 6. The system of claim 3, wherein thepressure controller is selected from the group consisting of: aproportional-integral controller; a proportional-integral-differentialcontroller or a proportional-differential controller.
 7. Apressurization control system comprising: an air supply; a first damperfluidly coupled to the air supply duct and configured to deliver a mainair flow directly to a room, the room comprising a closeable doorway,the first damper having a first operating range that includes adeadband; a second damper fluidly coupled to a second air supply ductand configured to deliver a supplemental air flow directly to the room,the supplemental air flow being separate from the main air flow, thesecond damper having a second operating range that corresponds to thedeadband; a room controller configured to generate a first controlsignal and a second control signal, the generation of the first controlsignal comprising selection of a control scheme from a plurality ofcontrol schemes the selection of the control scheme from the pluralityof control schemes comprising selection of a high-flow feedback controlscheme, a low-flow feedback control scheme, or a pressure feedbackscheme to be run for a period of time, wherein in a first configuration,the first control signal drives the first damper to a positioncorresponding to the deadband, and when air pressure within the roomcorresponds to the deadband, the second control signal drives the seconddamper to a position corresponding to the second operating range, andwherein in response to the closeable doorway opening and the airpressure within the room increasing, the second control signal drivesthe second damper towards a closed position, and when the air pressurewithin the room exits the deadband, the first control signal drives thefirst damper towards a closed position until a low flow limit isreached.
 8. The system of claim 7, wherein the first damper is a coarsecontrol valve, and wherein the second damper is a fine control trimvalve.
 9. The system of claim 7, wherein the room controller includes anincremental controller and a pressure controller.
 10. The system ofclaim 9, wherein the incremental controller is configured to generatethe first control signal, the first control signal being an incrementalflow signal communicated to the first damper, and wherein the pressurecontrol is configured to generate the second control signal, the secondcontrol signal being a pressure control signal communicated to thesecond damper.
 11. The system of claim 10, wherein the pressure controlsignal is generated as a function of a pressure set point and a roompressure measurement.
 12. The system of claim 1, wherein the room is alaboratory.
 13. A pressurization control system configured to regulateair pressure within a room, the room comprising a closeable doorway, thesystem comprising: a first damper fluidly coupled to an air supply ductand having an operating range, the first damper configured to controldelivery of a main air flow directly to the room; a second damperfluidly coupled to a second air supply duct and configured to controldelivery of a supplemental air flow directly to the room, thesupplemental air flow being separate from the main air flow; and a roomcontroller configured to control the first damper and the second damper,the control of the first damper comprising selection of a control schemefrom a plurality of control schemes the selection of the control schemefrom the plurality of control schemes comprising selection of ahigh-flow feedback control scheme, a low-flow feedback control scheme,or a pressure feedback scheme to be run for a period of time, the roomcontroller configured, in a first configuration, to drive the firstdamper to direct the main air flow towards a deadband within theoperating range, and when the air pressure within the room correspondsto the deadband, to drive the second damper to direct the supplementalair flow towards a pressure set point for the room, the deadbandincluding the pressure set point for the room, wherein in response tothe closeable doorway opening and the air pressure within the roomincreasing, the room controller is configured to drive the second dampertowards a closed position, and when the air pressure within the roomexits the deadband, the first control signal drives the first dampertowards a closed position until a low flow limit is reached.
 14. Thesystem of claim 13, wherein the first damper is a coarse control valve,and wherein the second damper is a fine control trim valve.
 15. Thesystem of claim 13, wherein the room controller includes an incrementalcontroller and a pressure controller, the incremental controllerconfigured to control the first damper, and the pressure controllerconfigured to control the second damper.
 16. The system of claim 15,wherein the pressure controller is configured to control the seconddamper as a function of the pressure set point for the room and a roompressure measurement.
 17. The system of claim 1, wherein the air supplyis fluidly coupled to a main air outlet via the first damper, the mainair outlet configured to deliver the main air flow to the room, andwherein the air supply is fluidly coupled to a supplemental air outletvia the second damper, the supplemental air outlet configured to deliverthe supplemental air flow to the room.
 18. The system of claim 1,wherein in the first configuration, the operating range of the seconddamper corresponds to the deadband within the operating range of thefirst damper.
 19. The system of claim 1, wherein the room is a firstroom, the air supply is a first air supply, and the room controller is afirst room controller, wherein the pressurization control system furthercomprises a first air delivery system and a second air delivery system,the first air delivery system comprising the first damper, the seconddamper, and the first room controller, the second air delivery systemcomprising: a third damper fluidly coupled to a second air supply andhaving an operating range, the third damper configured to controldelivery of a main air flow to a second room, the second room beingconnected to the first room via the closeable doorway; a fourth damperhaving an operating range, the fourth damper fluidly coupled to thesecond air supply, the fourth damper configured to control delivery of asupplemental air flow to the second room, the supplemental air flow tothe second room being separate from the main air flow to the secondroom; and a second room controller configured to provide a third controlsignal to the third damper and a fourth control signal to the fourhdamper, and wherein in a second configuration, the third control signaldrives the third damper to direct the main air flow to the second roomtowards a deadband within the operating range of the third damper, thedeadband within the operating range of the third damper including apressure set point for the second room, the pressure set point for thesecond room being greater than the pressure set point for the firstroom, and when the air pressure within the second room is within thedeadband within the operating range of the third damper, the fourthcontrol signal drives the fourth damper to direct the supplemental airflow to the second room towards the pressure set point for the secondroom, and the third control signal maintains a position of the thirddamper constant to hold the main air flow to the second room constant.